ḤESHWAN (MARḤESHWAN):

The eighth month in the Hebrew calendar. The name is not found in the Bible, since it was introduced after theBabylonian exile, as were the Hebrew names of the other months now in use. "Ḥeshwan" is an arbitrary shortening of "Marḥeshwan," which is the Assyrian "Araḥsamnu" (eighth month; see Delitzsch, "Assyrisches Handwörterb."). The name is found in the Targumim (Jastrow, "Dict.") and in Josephus ("Ant." i. 3, § 3). According to R. Eliezer (R. H.), the 17th of Ḥeshwan was the beginning of the Flood, but according to R. Joshua it began in Iyyar. Ḥeshwan contains sometimes 29, sometimes 30, days. The Biblical name for the eighth month is Bul.